The main drive shafts of aircraft gas turbine engines are subject to mass imbalance due to manufacturing variations. The shafts must be balanced prior to assembly in the engine in order to reduce shaft vibration during engine operation.
Shaft imbalance is characterized by a magnitude of imbalance and an angular direction of imbalance. The magnitude of imbalance caused by an eccentric rotating mass, is a function of the weight of the mass and the radial distance of the mass from the axis of rotation. The angular direction of imbalance is determined by the angular position of the eccentric mass relative to an arbitrary reference direction.
Due to the subsequent operations of an aircraft turbine engine assembly, there is often a need for further balancing of the rotating parts when the engines are completed. Further balance adjustment however, is normally difficult due to the inaccessibility of the rotating parts and, quite frequently, the unbalance is so severe that it is necessary to strip the turbine engines for rebalancing.
Therefore, there is a need for an improved balancing apparatus for the shafts of aircraft turbine engines which will enable a shaft to be balanced accurately and simply and which will permit simplified final adjustment after the aircraft engine has become completely assembled.